Frozen carbonated beverages (also known as FCBs) were invented in the 1950s in the USA by Omar Knedik. They are typically semi-frozen in a slush state, and can be eaten with a spoon, or other utensil, and in some cases sucked through a straw. A common FCB is the Slurpee™, which comes in a variety of different flavours and is typically sold at convenience stores. The FCBs are typically made with a syrup which is similar (or in some cases the same as) to the syrup used in regular non-frozen beverage dispensers. In many cases, an emulsifier is added which also helps to prevent the FCB mixture from solidifying when cooled.
Dedicated FCB machines have been implemented which dispense the FCB at the point of sale. The FCB machines have the syrup, water, and CO2 added, which is then mixed and cooled, typically below 0° C. and in most cases to approximately −3° C. The mixture is typically constantly stirred, and scraped from the edges of the chamber it is mixed in, to prevent the mixture solidifying when cooled.
Some FCB machines have a two stage process and others a single stage process. In a two stage process, the gas/liquid mixture is mixed/blended in a blend tank and is then fed to a freezing chamber where the temperature is lowered until ice crystals form in the liquid (and stirred as described above). In a single stage process, the constituents of the gas/liquid mixture are fed directly via valves into a header block and then straight into the freezing chamber.
A common problem associated with FCB machines is that, as the FCB is dispensed, the quantity of FCB within the machine is decreased, and fresh mixture is required to be added to the freezing chamber. Measuring the quantity of mixture, or quantity of the gas/liquid constituents, is important and is typically performed using one of two methods; namely pressure or gravity. In the case of a pressure method, a pressure transducer is provided that measures the pressure in the freezing chamber. As the FCB is removed, the pressure drops and more syrup, water, and CO2 mixture is added to the freezing chamber. Typically a float is provided that floats on the FCB surface and as the FCB is removed, the float lowers. The height of the float (or angle of the float relative to a fixed point) is measured and when it reaches it certain level, more syrup, water, and CO2 mixture is added to the freezing chamber.
Both of these methods have inherent problems that compromise their accuracy. As the CO2 is mixed and absorbed into the water/syrup mixture, the volume of the mixture changes. This change in volume affects both the pressure in the chamber and the level of the FCB in the chamber resulting in the pressure or gravity measurements changing as the CO2 is mixed and absorbed. This can alter the ratio of gas (CO2) to liquid (water and syrup) in the mixture, which can result in inconsistencies in the FCB being dispensed.
It is an aim of this invention to provide an improved beverage dispenser which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.
It will be clearly understood that any reference herein to background material or information, or to a prior publication, does not constitute an admission that any material, information or publication forms part of the common general knowledge in the art, or is otherwise admissible prior art, whether in Australia or in any other country.